It is well known to sort pieces of scrap metal according to metal type by melting the commingled scrap until the type of metal with the relatively lower melting temperature melts, thus separating it from the remaining commingled metal scraps. Considerable energy, however, is required to heat the scrap particles. Moreover, recovery is reduced because some of the particles become coated with other melted metals during the process.
It is also known to utilize image processing systems to sort articles by size, shape, and/or color. However, existing image processing sorting systems require that the articles to be sorted are conveyed in a specific orientation through the system and/or consist of a uniform size and shape. Existing systems typically "scan" the image to identify objects matching certain pre-defined shapes. This method of processing the image is often time-consuming. Moreover, the speed of processing is dependent upon the complexity of shape, as well as the number of objects in the image. This approach is particularly problematic when attempting to sort scrap particles which are unpredictably irregular in size and shape.
Another limitation to existing image processing sorting systems is the difficulty in maintaining consistent, even illumination of the viewing area through which the particles are conveyed.
Another drawback of existing image processing sorting systems is the difficulty in maintaining a uniform contrasting background to the particles.
Another drawback of the existing image processing sorting systems is that the efficiency of the system is affected by variations in the conveyor speed due to, for example, mechanical problems such as slippage.